Looking at the position of some of the holes the gearbox pivots at the top and the front set would be for a slimline with the extra bottom mount the widelines didn't have.
BSAOWNER, you haven't indicated what sort of Norvin you have, single. standard twin or twin with the gearbox chopped off (if so what gearbox) also single and twin Norton frames have different front mountings so that is a minimum of 6 different combinations.
I worked for several years part time making "Converta" plates so I'm fairly familiar with them, Unity never made single or chopped engine plates by the way.
As an aside there were at least 12 different "Triton" patterns depending on frame, engine, gearbox, alt/dynamo, unit/pre-unit combinations.
Chris.